Windows 10 is scheduled to be released to the public on 29 July 2015 -- just two days from now. Through Windows Insider Preview, I have been able to test Windows 10 on the Dell Latitude D620, with both Intel and Nvidia models covered, but on 32-bit Windows for the purpose of using i8kfangui (which I can confirm is compatible with Windows 8, 8.1, and 10). 64-bit Windows will encounter problems with the unsigned fanio driver; this has been an issue since Windows Vista. I recommend using 32-bit Windows 10 on these computers, even if your system has the 64-bit Core 2 Duo CPU, unless you need 64-bit for your applications.

If you decide to install Windows 10 on your Latitude D620, keep in mind that you should have at least 2 GB RAM, and 60 GB hard drive space available. Most D620s should need upgrades to meet these requirements. Additionally, users of Nvidia graphics should go into BIOS setup and disable LCD panel expansion; display scaling greatly slows down Windows setup, as the visual effects take much longer to process when panel expansion is enabled.

On my Intel graphics system, I had been using Windows 10 since build 9879 in late December 2014. Even on such an early build, I encountered few problems. A since-fixed bug involving the keyboard status lights not working did affect my system. I upgraded to build 9926 via Windows Update, which resolved the keyboard issue. I used a DVD of Windows 10 Pro to update my system to build 10240, which is the RTM (not Preview) build, which preserved my programs and settings. The graphics driver can be obtained through Windows Update; alternatively, the Intel 945GM driver for Windows 7 can be downloaded here from Intel's website. The driver works in Windows 8.1, and should work in Windows 10 as a result. If not, run it in Compatibility Mode for Windows 7. While Intel's chipset graphics struggle with just about any 3D game, performance in Windows is acceptable and all visual effects are snappy.

The Nvidia graphics system was not as compliant. The recommended Dell display driver R180799, using Nvidia Forceware 174.31, will install properly under Compatibility Mode, but problems quickly become apparent. Accessing the Start Menu results in elevated CPU load, flickering icons, then eventually the Start Menu closing itself. Metro apps are not stable, and crash upon starting; this includes Edge. Windows 8 is also affected by these issues; Windows 7 is not. Through the installation of Dell's driver R160485 for 32-bit Windows Vista, which uses Nvidia Forceware 101.44, users of Windows 8 report proper functioning. I have tested this on Windows 10, and can confirm that it does work properly; use R160485 in Windows 8 and 10.

"you should have at least 2 GB RAM, and 60 GB hard drive space available. Most D620s should need upgrades to meet these requirements" well, you would need to upgrade the RAM, since they shipped with 256MB to 1GB, but they shipped with 60 to 80GB HDDs, so you should be good to go there.

What about thermal output, can you tell how it compares in Win10 to Win7? Is performance any decreased compared to Win7?

"you should have at least 2 GB RAM, and 60 GB hard drive space available. Most D620s should need upgrades to meet these requirements" well, you would need to upgrade the RAM, since they shipped with 256MB to 1GB, but they shipped with 60 to 80GB HDDs, so you should be good to go there.

If you do an upgrade from a 60 GB hard drive, running out of space is a real concern. A bare minimum of ~11 GB free hard drive space is required to upgrade successfully, since Windows occupies 10 GB hard drive space on my system.

CalebHansberry wrote:What about thermal output, can you tell how it compares in Win10 to Win7? Is performance any decreased compared to Win7?

The Nvidia model has had problems continuously, I'm looking into those but it renders most programs too slow to use (elevated CPU load, Windows refusing to acknowledge the CPU speed properly, etc.). My Intel model has worked wonderfully, it is very responsive and I have yet to run into any problems. Idle CPU load is a bit higher so temperatures while idle will be elevated.

Windows 10, on startup, uses about 1 GB RAM; this leaves about 800 MB available for programs to use on 2GB computers.